1. Field of Invention
The present invention relates generally to a three-dimensional (3D) model having image-based lighting in a computer rendering environment and specifically to a method, apparatus, and system for live editing and local control of the 3D model.
2. Description of Related Art
Computer rendering is a process used to generate images of 3D models. The goal is often an image of the digital model that looks like a photograph of the real object in the real world. This particular instance of rendering is called photorealistic rendering. Other instances of rendering include stylistic rendering for illustration purposes.
Computer generated imagery of 3D models include a description of both the materials and lighting of the 3D model. The description of the materials include how the light reflects in different directions as it strikes a specific part of the 3D model. The description of the lighting can be given as light sources emitting the lighting onto the 3D model. A specific type of light source is image-based lighting.
Image-based lighting is a 3D rendering technique which involves capturing an omni-directional representation of real-world light information as an image, typically using a specialized camera. This image is then projected onto a dome or sphere analogously to environment mapping, and for this is used to simulate the lighting for the objects in the scene. This allows highly detailed real-world lighting to be used to light a scene, instead of trying to accurately model illumination using an existing rendering technique. Image-based lighting often uses high dynamic range imaging for greater realism, though this is not universal. Almost all modern rendering software offers some type of image-based lighting, though the exact terminology used in the system may vary. Image-based lighting is also starting to show up in video games as video game consoles and personal computers are starting to have the computational resources to render scenes in real time using this technique.
Image-based lighting includes an image that represents the lighting of the 3D model. This image that is used to represent the lighting can be used to represent a distant lighting environment such as a distant sphere, and each pixel in the image corresponds to a specific location on this distant sphere. The values of the pixels in the image correspond directly to the intensity of the lighting from that location.
Lighting in the real world can have intensities spanning multiple orders of magnitude. As such, the image used to represent the lighting will typically be a high dynamic range image where each pixel can represent more than the traditional 256 intensities. For example, the image used to represent the lighting can have each pixel being represented by a 32 bit floating point number. The 32 bit floating number makes it possible to represent more than 37 orders of magnitude of lighting intensities.
A problem with existing image-based lighting is that it is difficult to setup, modify or adjust the lighting to achieve a desired illumination of the 3D model. While conventional tools exist for creating image based lighting, there is no existing solution that offers a direct integration of a 3D rendering system with an image based lighting system where the lighting information can be transferred from the 3D rendering system to the editor and back. Existing systems only allow for transferring images to the rendering application and not from the rendering system. The ability to transfer lighting from the rendering application to the editor is critical to allow for small adjustments and fine-tuning of the lighting rather than starting from scratch. Being able to transfer both to and from the 3D rendering system would make the editor an integrated component of the rendering application with a natural and fast method for adjusting the image based lighting environment. Of critical importance is the ability to interactively view a 3D model illuminated by the image based lighting environment as it is being edited.
U.S. Pat. No. 6,983,082 to Duiker is directed to a reality-based light environment for digital imaging in motion pictures. Duiker uses image-based lighting in the rendering of digital objects derived from image data collected from a real motion-picture set. The image data includes sets of correlated images at different exposure levels, each corresponding to a selected location. The image data is processed to define an extended dynamic range panoramic image for each selected set location. The image data is color and intensity corrected based on a scaled reference object. Although Duiker's system includes image-based lighting, Duiker's system does not integrate with an editor or adjust local portions of a 3D model.